Passive smoking and chronic obstructive pulmonary disease mortality: findings from the Japan collaborative cohort study

Objectives: To elucidate the association between passive smoking at home and chronic obstructive pulmonary disease (COPD) mortality via a large-scale nationwide cohort study in Japan. Methods: Never smokers (n = 34,604) aged 40–79 years at baseline (1988–1990; 4884 men, 29,720 women) were included in the analysis. Passive smoking at home was measured based on self-reported frequency of weekly exposure to passive smoking at home. An inverse probability of treatment-weighted competing risk model was used to calculate the hazard ratio (HR) and 95% confidence interval (CI) for COPD mortality. Results: During a median follow-up of 16.4 years, 33 participants (10 men, 23 women) died of COPD. The HR for participants exposed to passive smoking at home ≤4 days per week or those who had almost daily exposure to passive smoking at home had a significantly increased risk of COPD mortality (HR 2.40, 95% CI 1.39–4.15, HR 2.88, 95% CI 1.68–4.93, respectively). Conclusions: The present findings suggest that avoiding passive smoking at home may be beneficial for preventing death due to COPD among never smokers.